The mother of Boston Marathon bomber Tamerlan Tsarnaev knew as early as 2011 that her son had been radicalized and sent text messages to family in Russia suggesting he was willing to die for Islam, the FBI told lawmakers this week according to two officials with knowledge of the Capitol Hill briefing.

Tsarnaev, who was killed days after the April 15 bombing in a shootout with police, is said to have embraced radical Islam in recent years and recruited his younger brother, Dzhokhar Tsarnaev, to carry out the attack that killed three and wounded more than 180 near the finish line of the world's most prestigious road race.

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Dzhokhar Tsarnaev was caught alive but wounded on Friday and charged with use of a weapon of mass destruction, for which he could get the death penalty.

The FBI filed a federal criminal complaint against the 19-year-old on Sunday, and federal District Court Judge Marianne Bowler arrived at the hospital where he is being treated to preside over his initial hearing Monday, when she read him his Miranda rights.

[FBI officials told The Associated Press Wednesday that Tsarnaev acknowledged to investigators his role in the attacks before he was advised of his constitutional rights. He reportedly said he was only recently recruited by his brother to be part of the attack.]

But Fox News' sources say there was confusion about Bowler's timing, with some voicing concerns that investigators were not given enough time to question Dzhokhar under the "public safety exception" invoked by the Justice Department.

Two officials with knowledge of the FBI briefing on Capitol Hill said the FBI was against stopping the investigators' questioning and was stunned that the judge, Justice Department prosecutors and public defenders showed up, feeling valuable intelligence may have been sacrificed as a result.

The FBI had been questioning Tsarnaev for 16 hours before the judge called a start to the court proceeding, officials familiar with the Capitol Hill briefing told Fox News. Moreover, the FBI informed lawmakers that the suspect had been providing valuable intelligence, but stopped talking once the magistrate judge read him his rights.

But Justice Department spokesman Dean Boyd disputed the claims, saying that the suspect’s initial appearance was scheduled following the filing of the criminal complaint in a manner “consistent” with procedure – and that the agents were aware.

“The Rules of Criminal Procedure require the court to advise the defendant of his right to silence and his right to counsel during the initial appearance. The prosecutors and FBI agents in Boston were advised of the scheduled initial appearance in advance of its occurrence,” Boyd said.

A federal law enforcement official also told Fox News that the courts, not the Justice Department, made the decision on when and where to hold the hearing.

“The (FBI) agents and prosecutors were notified beforehand,” the official said, claiming those agents had already left the room when the judge came in.

The exact timeline is unclear. A transcript of the court proceeding shows Bowler asking a doctor if Tsarnaev was "alert."

"You can rouse him," she says in the transcript.

"How are you feeling? Are you able to answer some questions?" the doctor asks Tsarnaev, who nods.

Although Bowler advised Tsarnaev, an ethnic Chechen and U.S. citizen, of his Miranda rights, it remains to be seen whether anything he told investigators before Bowler arrived can be admitted as evidence against him -- or whether such interrogations would even be needed to convict him, given the amount of other evidence referenced in the criminal complaint signed by FBI Special Agent Daniel Genck.

Some Republican lawmakers have criticized the Obama administration for deciding against treating Tsarnaev as an enemy combatant, which would allow more time for interrogating him. The public safety exception to Miranda lasts only 48 hours.